The present invention relates to eyeglasses which are weighted for balancing or counterbalancing purposes and more particularly to such eyeglasses which have improved fitting facility together with a method for fitting the same.
"Eyeglasses" is a general term intended to embrace optical devices containing corrective lenses for defects in vision or lenses for such special purposes or filters for absorbing portions of the light spectrum, providing physical shields for the eyes, or making available other physical or optical functions for protective or visual assisting purposes.
A normal, or emmetropic, eye focuses light rays from distant objects on the retina by means of complementary deflections of the cornea, lens and fluid of the eye. Such deflections result from light passing from one light transmitting material to another having a different optical density.
Unfortunately, few eyes are so precise in their refractory ability as to produce a sharp retinal image at all reasonable distances. The defects impairing vision may be in curvatures, densities and positions of the eye structures; in variations in the length of the eye ball; in abnormal visual axes; in disparity in the optical characteristics of a person's two eyes; or in defects in ocular movement or control caused by muscle imbalance or failure of coordination.
Much has been done with eyeglasses to correct or ameliorate these and other causes of visual impairment; however, no matter how accurate the diagnosis and precisely appropriate the optical correction, unless the eyeglasses can be maintained in proper relation to the eyes during use the desired coordinated optical reflections are not properly attained.
The present invention resulted from the recognition that much of the impairment of the performance of eyeglasses stemmed from poor balance of the glasses and improper fitting, frequently resulting from accidents during use. It was further recognized that because of the ocular pieces or lenses, the lens frames and the nose bridges of eyeglasses, their centers of gravity were too far toward tending to make them slip down on the wearer's nose or even to fall. The extent of the imbalance can be visualized by thinking of the usual eyeglasses' temples as rested on the wearer's ears as fulcrums. Thus, the weight of the lenses, lens frames, and bridge has a substantial lever arm from such fulcrum making the maintenance of proper fitting understandably difficult.
It was then discovered that such eyeglasses had temples which were extended past a wearer's ears and provided with weights rearwardly of the ears, the weights of the lenses, lens frames and bridges were effectively counterbalanced and fitted position much more effectively and dependably maintained. This was found to be true even if the eyeglasses were not counterbalanced to the extent of actually being balanced on the ears. Since the lenses, lens frames and bridge exert their weight through a much longer lever arm than the weights on the rearwardly extended ends of the temples, it is desirable that the temple weights be substantial in relation to the weight they counterbalance but they need not fully balance on the ears as fulcrums, even partial counterbalancing being of marked advantage.
However, it was soon discovered that the provision of weights on the rearwardly extended ends of the temples interfered with the bending of such temples in the proper fitting of the eyeglasses to the patient.
The present invention has made possible the provision of eyeglasses which have provided temples having weighted rearwardly extended ends which counterbalance the weight of the lenses, lens frames and bridge of such eyeglasses without impairing the proper fitting of the eyeglasses.